In the catalytic cycle of these enzymes, a molecule called a substrate binds to the enzyme. This leads to a process called oxidation. The enzyme's structure has a confined space that allows it to act like as a sensor and a soft robot. It interacts with the substrate using weak interactions, like soft impacts. These interactions transfer energy, causing parts of the enzyme and the molecules inside it to move. This movement generates ultimately a special substance called oxoiron species, which serves the enzyme to oxidize a variety of different substances.